August 2, 1964 - Gulf of Tonkin - The North Vietnamese fire on a U.S. destroyer anchored in the Gulf of Tonkin. After President Lyndon Johnson falsely claims that there had been a second attack on the destroyer, Congress passes the Gulf of Tonkin resolution, which authorizes full-scale U.S. intervention in the Vietnam War. Johnson orders the bombing of North Vietnam in retaliation for the Tonkin "attack."
August 5, 1964 - President Lyndon B. Johnson asks Congress for the power to go to war against the North Vietnamese and the Communists for violating the Geneva Accords against South Vietnam and Laos. The request is granted August 7, 1964 in a Congressional joint resolution.
January 30, 1968 - Tet Offensive - The North Vietnamese launch a massive surprise attack during the festival of the Vietnamese New Year, called Tet. The attack hits 36 major cities and towns in South Vietnam. Both sides suffer heavy casualties, but the offensive demonstrates that the war will not end soon or easily. American public opinion against the war increases and the U.S. begins to reduce the number of troops in Vietnam.
March 16, 1968 - My Lai Massacre - About 400 women, children and elderly men are massacred by U.S. forces in the village of My Lai in South Vietnam. Lieutenant William L. Calley, Jr., is later court-martialed for leading the raid and sentenced to life in prison for his role but was released in 1974 when a federal court overturns the conviction. Calley is the only soldier ever convicted in connection with the event.
April 1970 - Invasion of Cambodia - President Richard Nixon orders U.S. and South Vietnamese troops to invade border areas in Cambodia and destroy supply centers set up by the North Vietnamese. The invasion sparks more anti-war protests, and on June 3, 1970, Nixon announces the completion of troop withdrawal.
May 4, 1970 - National Guard units fire into a group of demonstrators at Kent State University in Ohio. The shots kill four students and wound nine others. Anti-war demonstrations and riots occur on hundreds of other campuses throughout May.
February 8, 1971 - Invasion of Laos - Under orders from President Nixon, U.S. and South Vietnamese ground troops, with the support of B-52 bombers, invade southern Laos in an effort to stop the North Vietnamese supply routes through Laos into South Vietnam. This action is done without consent of Congress and causes more anti-war protests in the U.S.
January 27, 1973 - A cease-fire is arranged after peace talks.
March 29, 1973 - The last American ground troops leave. Fighting begins again between North and South Vietnam, but the U.S. does not return.
April 30, 1975 - South Vietnam surrenders to North Vietnam as North Vietnamese troops enter Saigon, now called Ho Chi Minh City.
May 25, 2012 - President Barack Obama signs a proclamation that puts into effect the Commemoration of the 50th Anniversary of the Vietnam War that will continue until November 11, 2025. Over the next 13 years, the program will "honor and give thanks to a generation of proud Americans who saw our country through one of the most challenging missions we have ever faced."
May 15, 2013 - As of this date 1,647 soldiers remain unaccounted for.